Acute lower extremity running kinematics after a hamstring stretch.

Context: Limited passive hamstring flexibility might affect kinematics, performance, and injury risk during running. Preactivity static straight-leg raise stretching often is used to gain passive hamstring flexibility.

Objective: To investigate the acute effects of a single session of passive hamstring stretching on pelvic, hip, and knee kinematics during the swing phase of running.

Design: Randomized controlled clinical trial.

Setting: Biomechanics research laboratory.

Patients Or Other Participants: Thirty-four male (age = 21.2 ± 1.4 years) and female (age = 21.3 ± 2.0 years) recreational athletes.

Intervention(s): Participants performed treadmill running pretests and posttests at 70% of their age-predicted maximum heart rate. Pelvis, hip, and knee joint angles during the swing phase of 5 consecutive gait cycles were collected using a motion analysis system. Right and left hamstrings of the intervention group participants were passively stretched 3 times for 30 seconds in random order immediately after the pretest. Control group participants performed no stretching or movement between running sessions.

Main Outcome Measure(s): Six 2-way analyses of variance to determine joint angle differences between groups at maximum hip flexion and maximum knee extension with an α level of .008.

Results: Flexibility increased between pretest and posttest in all participants (F(1,30) = 80.61, P < .001). Anterior pelvic tilt (F(1,30) = 0.73, P = .40), hip flexion (F(1,30) = 2.44, P = .13), and knee extension (F(1,30) = 0.06, P = .80) at maximum hip flexion were similar between groups throughout testing. Anterior pelvic tilt (F(1,30) = 0.69, P = .41), hip flexion (F(1,30) = 0.23, P = .64), and knee extension (F(1,30) = 3.38, P = .62) at maximum knee extension were similar between groups throughout testing. Men demonstrated greater anterior pelvic tilt than women at maximum knee extension (F(1,30) = 13.62, P = .001).

Conclusions: A single session of 3 straight-leg raise hamstring stretches did not change pelvis, hip, or knee running kinematics.